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Evolution. Fossils indicated that living things have changed. Several scientists had ideas to explain how. 1) Lamarck. French scientist Late 1700’s- early 1800’s “acquired traits” theory: traits are not determined by genes but by “need”
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Fossils indicated that living things have changed. Several scientists had ideas to explain how.
1) Lamarck • French scientist • Late 1700’s- early 1800’s • “acquired traits” theory: traits are not determined by genes but by “need” EX: giraffe necks grow longer because they stretch to reach the leaves higher up.
2) Charles Darwin • English scientist • Developed his theory of “natural selection” in the mid 1800’s • Was a naturalist on the HMS Beagle (traveled around the world, mostly the southern hemisphere) for 5 years.
Darwin Noticed organisms had some similarities even when they lived far apart. * Darwin’s Finches Kept records & collected specimens Published “The Origin of Species…”
Good example of how evolution occurs Each Galapagos Island has its own unique species of finch Each finch had a head and body well-adapted for life on that island The finches were different species, but looked similar Darwin’s Finches
Darwin realized that the finches had a common ancestor • He proposed that originally a few seed-eating finches had flown to the islands from mainland. Over millions of years, the finches adapted to the foods available on each island – and evolved into separate species.
Darwin’s ideas that served as a basis for theory of natural selection 1. All organisms produce more offspring than can survive. 2. Population numbers remain fairly constant over long periods of time. 3. Organisms in a species show wide variation. 4. Some variations are inherited and passed on to the next generation.
Units of Variation • Genes carry inheritable characteristics, also source of random variation – crossing over • Mutations cause variation – missing letters in DNA
Then Darwin made 2 deductions: • Since most offspring don’t survive, all organisms must have to struggle for survival. (Others are eaten, or die of disease.) • The ones who survive and reproduce will pass on their genes.
Mutations play big role in natural selection Rabbit Tale - Maybe once upon a time all rabbits had short ears and managed OK.
Then one day a mutant with big ears was born. She was always the first to dive for cover. Pretty soon, she had babies; some inherited her big ears. They all dived for cover as fast as their mom – faster than the short earred rabbits. Eventually, only the big earred rabbits are left.
Natural Selection Nature selects those that are best adapted to survive. “Survival of the Fittest” Any adaptive advantage (a favorable trait) that an organism has is passed to offspring.
Example of evolution through natural selection Cockroaches Over the centuries, as man and cockroaches have shared homes, cockroaches have become smaller and flatter – easier access to hiding places. (Large, fat ones more easily stomped.)
Another example - antibiotic resistance by natural selection • Someone gets sick • Give them antibiotics • 99% of the bacteria are killed; only the antibiotic resistant mutants survive • They thrive and flourish • Person gets sick again • Bacteria cannot be killed by antibiotics
Artificial Selection • Breeding for certain traits • Environment is very easy – all organisms survive • Breeder for (selects) the trait he or she Wants in offspring Ex – color, size
Evidence of Evolution • Fossils • Similarity of embryos • Homologous and analogous structure • Vestigial structures • Similarities in macromolecules
Fossils – tell us that organisms that once lived on Earth are not here any more.
Homologous Structures – similar structures with similar functions. Suggest a common ancestor.
Analogous Structures Structures in unrelated organisms that carry out same functions: EXs - Kidneys in mammals and Malpighian tubules in insects Lungs in mammals and gills in fish Wings of insects and wings of birds
Vestigial Structures • Examples: appendix, wisdom teeth, human tail bone • Interpretation: the vestigial structure was functional in some ancestor of the modern organism • Snakes have pelvic bones; they are known to be the descendants of four-legged reptiles.
Vestigial features.The skeleton of a baleen whale, a representative of the group of mammals that contains the largest living species, contains pelvic bones. These bones resemble those of other mammals, but are only weakly developed in the whale and have no apparent function.
Beneficial mutations give: rise to new genetic traits (adaptive traits) that give an organism an advantage in a changing environment and produce more offspring with those traits - natural selection. Through time these adaptive traits become more prevalent in a population. Evolution is the change in genetic makeup of a population through successive generations. New species can be formed, or is life forms cannot adapt they will decline or become extinct. Biodiversity is a result of the ongoing processes of evolution and extinction. Biodiversity sustains life and provides genetic raw material for adaptation to future changes in environmental conditions
Divergent and Adaptive Radiation • Adaptive radiation – many related species evolve from a single ancestral species Examples: Galapagos tortoises, finches – diverged in response to food source • Beak differences in Hawaiian honeycreepers
Near losses… • The cheetah, Acinonyx jubatus, is the sole member of its genus. Twenty thousand years ago, cheetahs roamed throughout the savannahs and plains of four continents: Africa, Asia, Europe, and North America. About 10,000 years ago - because of climate changes - all but one species of the cheetah, jubatus, became extinct. With the drastic reduction in their numbers, close relatives were forced to breed, and the cheetah became genetically inbred, meaning all cheetahs are closely related. • http://www.nyarugame.co.za/cheetahdivert.html
Loyola University, New Orleans • A genetic mutation in a five-year-old child from Berlin is responsible for his bulging well defined muscles. Dr. Schuelke, the boy's doctor since his birth says the youngster doesn't stand out on the playground, however, he can perform 'feats of strength' when he puts his mind to it. Dr. Schuelke tested the baby for mutations in the myostatin gene and found both copies of the gene were mutated. His body wasn't producing myostatin, which regulates muscle growth and muscle mass in humans.
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